Patent GB-977915-A (GB)
Title: Associative magnetic memory devices and matrices
Inventor: HARMAN MICHAEL GODFREY
IPC: G11C15/02
Filed: 1962-03-30
Abstract: 977,915. Digital data storage apparatus. NATIONAL CASH REGISTER CO. March 1,1963 [March 30, 1962], No. 12264/62. Heading G4C. [Also in Divisions H1 and H3] A magnetic storage element comprises a multi-apertured core of rectangular hysteresis material having two, interrogate windings and I 1 , an output being produced in a sense winding only if the element stores a binary one and one interrogate winding I 0  is pulsed, or the element stores a binary zero and the other interrogate winding I 1  is pulsed. The element is intended for use in an associative magnetic store, the production of an output in the sense winding being indicative of a mismatch between the stored binary digit and the corresponding digit of a reference number. Basic element. A ferrite core, Fig. 1, has a major aperture 1, writing apertures 2-5 threaded by an enable and write windings E, W 0 , W 1  and readout apertures having associated interrogate windings I 0 , I 1 , a detector and sense winding DS, and a restore winding Q, the interrogate winding I 0  also serving as a read winding R When energized alone the enable winding establishes fluxes about the writing apertures 2 to 5 as shown in Fig. 2A. To write a binary digit into the core the enable winding E and one write winding W 0  or W 1  are pulsed simultaneously, the flux condition produced when E and W 1  are pulsed being shown in Fig. 2B. If E and W 0  are pulsed the flux around the major aperture 1 passes in the reverse direction. The flux conditions at the read out apertures are shown in Figs. 3A to 3F. The restore winding Q is pulsed during writing and after reading, and the flux directions for the stored digits "0" and "I" are shown in Figs.. 3B and 3E respectively. If the interrogate winding I 1  is pulsed the flux conditions are changed to that shown in Figs. 3C and 3F for a stored "0" and "I" respectively. As the detector and sense windings DS has a figure of eight formation about aperture 7, a voltage will be induced therein only in the case of the change of flux pattern from that of Fig. 3B to that of Fig. 3C; Similarly if the interrogate winding I 0  is pulsed the flux conditions shown in Figs. 3A or 3B are obtained, and an output in winding DS is produced only in the instance of the core storing a "I" digit. Alternative basic element. A row of discrete elements is formed by an apertured ferrite strip 13, each element being constituted by the magnetic material about respective major apertures, 14, 14<SP>1</SP>,14<SP>11</SP>. Each element has writing apertures 15, threaded by bias and enable windings B, E and a writing aperture 16 threaded by a write winding W. The bias is continuous and is neutralised while the enable winding is energized. Consequently, as the write and enable windings are energized simultaneously, a flux 21 is established around the major aperture the direction of which depends on the current direction through the write winding. Read apertures 18, 19 are provided for each element, and reference apertures 17,17<SP>1</SP>,17<SP>11</SP> are located between the elements. These apertures are selectively threaded by a sensing winding S, a detection and reading winding DR, a permanently energized winding BQ producing reference fluxes about aperatures 17, and restore windings Q which are energized during writing and after read out. Interrogation is by windings I 0  and I 1  which produce clock-wise and anti-clockwise fluxes about apertures 18 and 19 respectively when energized. In the case of winding I 0  its clockwise magnetisation interacts with the clockwise reference flux about aperture 17 and the storage flux 21 passing between apertures 14 and 18. If a "I" is stored, as shown by the clockwise flux 21 in the left-hand element of Fig. 4, the clockwise I 0  magnetisation reverses the flux directions in the core portions between aperture 18 and apertures 14, 17 and induces a detector winding output. As the storage flux is oppositely directed for "0" storage, the flux reversal in the core portions is not possible and no output is produced. The winding I, functions similarly, and by producing an anticlockwise magnetisation in association with an anti-clockwise flux about the adjacent reference 17<SP>11</SP>, causes a detector winding output to be produced if an "0" is stored by the anti-clockwise flux 21. Energization of the Q windings restores the fluxes to their initial condition. Similar non- destructive read out of the stored information is obtained by pulsing the read and detector winding DR and detecting the induced output in the sense winding S. Associative storage matrix. A row of elements formed by a ferrite strip 30 and the associated circuitry is shown in Fig. 5A. The column circuitry for a single digit in each of strip elements 50 is shown in Fig. 5B. Each ferrite strip forms a word line and has printed enable E, read and detect RD and bias BQ windings. The enable and read and detector windings are connected through write and read drivers 31 and 35 respectively to constant current sources 32, 36. The read and detect winding RD is also connected through a rectifier 38 to a sense amplifier 39 and bi-stable unit 40. The constant current sources are connected to a by-pass circuit comprising rectifiers 33 and a constant voltage source 34. A bias source 41 is connected to winding BQ. The column circuits for a single digit in each word line, Fig. 5B, comprise a bias winding connected to a source 51, a restore winding Q connected to a restore driver 63, a write winding W selectively energized in one or the other direction by a write driver 57 in accordance with the digit to be written, a sense winding S connected through a sense amplifier 61 to a bistable unit 62 and interrogate windings I 1 , I 0  selectively energized by an interrogate driver 52. Constant current sources 55, 60, 64 and a by-pass circuit 56 is also used. A digit is written in a selected word line by simultaneously pulsing the appropriately enable and write windings E, W and the restore winding Q. Read out to the sense amplifier 61 is obtained when the read and detect winding is pulsed by driver 35. To compare a stored digit with a reference digit "0" or "I" the appropriate interrogate winding I 0  or I 1  is pulsed. If a mismatch is present an indication is given by the output induced in the read and detect winding RD and is indicated by sense amplifier 39. Modified storage matrix in which only that sense winding associated with a desired reference applies an output to its sense amplifier. The read and detect windings 70 for a binary reference number are shown in Fig. 6, the windings being connected in series with rectifier 71 and associated with read drivers D1-D4<SP>1</SP> and sense amplifiers SA1-SA3<SP>1</SP>. When interrogation takes place by energization of windings I 1  or I 0  (not shown), the mismatch outputs induced in winding 70 act in a direction opposite to the conductive sense of the rectifiers. At the same time a pulse is applied to each sense amplifier from a generator 73 of such a polarity that current flows through only those windings 70 in which a mismatch voltage is not induced. This arrangement is stated to reduce the number of circuit components.